I test-drove an IROC for a friend today. Here's the problem though:

My TA is a 305TPI/Manual w/ 67k miles
IROC was a 305TPI/Manual w/ 100k miles

The throttle response on the IROC was near-perfect. almost immediately after punching the pedal or pulling the throttle cable from within the engine bay, the car revved up. My TA does the same thing, but there's a NOTICABLE delay. What's the deal? my car's newer, less miles, and better maintained (tune up < 500miles ago)

I'm dreading the thought of it being my injectors ($$). what do u guys think it is? Anything i can do to make this car run (AT LEAST) like it should?

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http://www.tcnj.edu/~esposit3

• '89 Trans AM, 305 TPI, 5-spd
• '86 Firebird, 2.8, Auto

 

Check for vacuum leaks?
Fuel pressure OK? Fuel filter changed?
Spark plugs fouled?
Coil old?
Cap/rotor? Bad/old plug wires?
Air filter?
gummed MAF screens?

And the list continues...
It's probably simple...you can check the ECM for codes too, but it's hard to say when we don't know much about you car. Is your TPS and MAF any good? What did the tune up you got include?

 

sorry bout that, didn't want to make a long post of it initially:

my tuneup included:
plugs, wires, dist.cap, dist.rotor, pvc valve (or is it pcv? ), oil change, oil filter, fuel filter, air filter's a new K&N, fuel injector cleaner (just a bottle) 2 months ago.

I guess the best place to start then would be the TPS and MAF screens (i'm not getting any codes)

Thanks for jogging my memory, this is my first TPI car. If anyone's got any further advice, keep it comin'

 

Jim,

Do yourself a favor - leave the MAF screens alone. Check/set the TPS voltage, check the minimum air position of the throttle, check the base timing, and clean the IAC valve and IAC air passages.

If anything, check the ductwork and connections between the MAF and throttle body. If you wonder about MAF screen removal on a 305, search the archives for "MAF", "SCREEN", and "OH, SHlT, MY MAF IS DEAD".

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Later,
Vader
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"What a Day..."
Adobe Acrobat Reader

 

My '86 used to be the same way, then one day I read that the O2 needed to be changed every so often I just put it on my list....needless to say months later I got around to changing it and it made a very big difference...just a thought.

 

Ok, had about 5 free minutes today and noticed a coupla things:

- w/ ignition on the TPS reads .53 V, looks good to me, but....

- using my hand to rotate the throttle the highest it gets is 4.62 V. problem is neither the throttle cable (to the pedal) or the cruise control cable (no big deal) is capable of rotating the throttle assembly that far

- since it was only me trying to read my meter while also pressing the pedal from the driver's seat.. i estimate the pedal can only make the TPS go to about 3.8 V.

- the throttle cable's semi-limp and has about a 1/2" of give before it actually starts rotating the assembly

- so this is just ANOTHER small problem on top of my lagging response, right? judging from the posts i should fix this first w/ a new cable for +-$20 and work from there??

 

Vader why is removing the screens on a 305 bad why does the maf go.what's the difference between 305 and 350 maf in reference to removing the screens.i just removed the screens on my 87 305 tpi.It runs fine

 

SSGTA,

If you are very careful, you probably won't cause any damage to the hot wire sensor. However, the screens cause turbulence in the air flowing throught the sensor housing, which results in fairly equal air flow through the sampling tube and the remainder of the sensor body. With no screens, the air will tend to follow the path of least resistance. If there are curves or elbows in the ducting near the MAF, the air may be directed away from the sampling tube, resulting in incorrect MAF readings. There have been several examples on this board of people removing MAF screens and suddenly getting a code 33 or 34, depending on the orientation of the sensor and the intake ducts.

You might not have enough variation in the readings to cause an error code, and many people do this without having this problem. That doesn't mean that the MAF is reporting correctly, but is at least reporting within the limits of the PROM programming. You could be running very lean and not be able to determine why, and the ECM will report a code 44 without giving you a hint of the MAF problem.

The other reason to maintain the screens is that they protect the hot wire from sonic shock created by WOT howl and lean backfire. A couple of good pops in the intake are all it takes to toast a MAF hot wire.

Oddly, the whole thing may be unnecessary, since most 305s aren't built to require intake air flows beyond what the stock MAF can deliver without pressure drop across the sensor. Even most 350s do not require the extra flow. It would be like bolting an 850CFM Holley on a 350 street engine - everybody does it, but everybody wonders why they lost performance.

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Later,
Vader
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"What a Day..."
Adobe Acrobat Reader

[This message has been edited by Vader (edited April 14, 2001).]